State the purpose of hardware.
Hardware provides basic computing resources: CPU, memory, I/O devices.
State the purpose of the operating system.
The operating system controls and coordinates the use of hardware resources.
State the purpose of application programs.
Application programs define how hardware/OS resources are used to solve the computing problems of the users.
State the purpose of hardware resources used by the CPU to execute programs.
Memory to store both programs and data. Devices for input and output. Bus to transfer information between CPU and memory/devices.
What does the CPU do in the fetch-execute cycle?
Fetches and decodes next instruction. Generate control signals and operand information. Inside the execution unit, control signals select the functional unit and operation.
State the purpose of the three functional units.
Arithmetic logic unit - read one/two registers, perform operation, write result back. Branch unit - test condition and set value of program counter. Memory access unit - generate address and use bus to read/write value.
What is a bus?
Shared communication wires.
State an advantage of using buses?
Don’t need wires everywhere - low cost and versatile.
State a disadvantage of using buses?
Is a potential bottleneck.
State the 3 lines in a typical bus.
Address lines, Data lines, Control lines.
State the purpose of address lines.
Address lines determine how many devices are on bus. Note: devices includes memory addresses and memory-mapped devices.
State the purpose of data lines.
Data lines determine how many bits can be transferred at once.
State the purpose of control lines.
Control lines indicate target devices and selected operations.
Describe how the buses are used to communicate.
In an initiator-responder manner. Initiator puts address onto bus and asserts read. Responder reads address from bus, retrieves data, and push onto bus. Initiator reads data from bus.
State the characteristics that may differ between buses.
Data width, Max number of devices, Max length.
What are the 4 types of buses in the bus hierarchy?
Processor bus, Memory bus, PCI buses, Bridges.
State the purpose of processor bus.
Used by the CPU to talk to cache.
State the purpose of memory bus.
Used by CPU to communicate with memory.
State the purpose of PCI buses.
Used to communicate with devices.
State the purpose of bridges.
To bridge forward from one bus to another.
What is unique about the processor bus?
It is the fastest and widest bus.
Describe how the bootstrap program (bootloader) boots the computer.
BIOS/UEFI stored in ROM executes when the machine powers on. It initialises all parts of the system inc. memory and devices controllers. Finds, loads and executes the kernel. Starts the operating system.
Describe how the operating system starts in stages.
The kernel enables processes to be created, devices and file system to be accessed. System processes starts.
State the purpose of a device controller.
Each device controller is responsible for a particular device type. Controls interaction between the device and the local buffer.
